So what happens when he is genuinely sick, or you want a holiday together? Do they get someone else in, or is it a case of 'if you go, don't come back'?
I find it amazing that a company would rather work a critical employee into the ground such that they're actually in no fit state to work - if nobody else is available, and the employee is such a mission-critical asset to the firm that nobody else can do what they do, you should treat them as such.
Anyway, with regard to burn-out, here's some extracts from the report into an accident in the UK. The judge is describing the individual who made the fatal error:
"So far as his uncharacteristic errors are concerned... (snip) These are so uncharacteristic, so much a contradiction of his methodical working life that there has to be a further cause. I find that cause to be the constant repetition of weekend work in addition to work throughout the week which had blunted his working edge, his freshness and his concentration.
(snipped some more)
He, like many others, accepted every opportunity he was given to do overtime with the result that in the three months before the accident he had had one sole day off in the entire thirteen weeks. I find this to be totally unacceptable."
When was this written? 1988. The individual in question was burnt-out and made a simple error which killed thirty-five people. You might say it's a cop-out, but I'm sure the families of those 35 dead people wouldn't agree.
In the industry he was employed in there are now legal safeguards to limit hours (and number of consecutive days) worked. Jobs which require concentration, like driving, operating machinery, etc, have limits on their working hours because tiredness kills, though interestingly the health sector here doesn't have similar rules. Junior doctors in the UK are currently in a nationwide labour dispute regarding a proposal to increase their working hours and remove the few legal safeguards against excessive working hours that they have.
One of their messages: Tired doctors kill people.
I'd much rather have some time off and go on holiday than be dead through overwork by the time I'm 50.